This invention relates generally to cylinder locks and, more specifically, to pin tumbler cylinder locks.
Pin tumbler cylinder locks are used extensively in a wide variety of security applications. One such lock is disclosed in the applicant's co-pending U.S. application Ser. No. 706,935. The lock disclosed in that application includes a plug eccentrically mounted in a cylindrical housing and enclosed by a plurality of longitudinally aligned sleeve segments. The plug and sleeve segments together form a composite concentric plug unit that can be turned with a proper key which brings driver and tumbler pins to shear at the intersection between the sleeve segments and the cylindrical housing. The sleeve segments are provided with recesses that emcompass the pinways and form false shear levels that help subvert picking of the lock. Although hightly resistant to picking, the lock described in the abovenoted application does exhibit features that could be detrimental under certain circumstances. For example, after managing to ledge all driver pins on recess surfaces of the sleeve segments, one could possible breach security of the lock by pulling the plug directly out of the cylinder housing. Also under highly unusual circumstances the lock might be violated by the use of a procedure related to the well-known technique of impressioning. The object of this invention, therefore, is to provide an improved, pick-resistant pin tumbler cylinder lock.